Piston



Oct. 6, 1931. G. E. FRANQUIST 1,826,171

PISTON Filed May 26, 1922 2 Sheets-Sheet 1 ZINVENTOR.

Oct. 6, 1931. FRANQUIST I 1,826,171

PISTON Filed May 26 1922 2 Sheets-Sheet 2 Ba 7 I I 8 Mi; 5 d

lzvvzl qmv Gustave E n Frangulsl' Patented Oct. 6, 1931 UNITED STATES PATENT- OFFICE GUS TAVE E. FRANQUIST, OF ROCHESTER, NEW YORK; MARGARET LOUISE FRANQUIST,

EXECUTRIX F SAID GUSTAVE E. FRANQUIST, DECEASED, ASSIGNOR TO THE CLEVE- LAND TRUST COMPANY, OF CLEVELAND, OHIO PISTON Application filed May 26,

' ment on my earlier piston on which U. S.

Letters Patent No. 1,153,902 was granted and relates to any type of piston having a head and a skirt, and in which said head and skirt are separated partially or otherwise on the peripheral surface by a circumferential slot or groove. on the belief that very largely the trouble experienced with pistons prior to that time, under operating conditions was due, not to the relatively large expansion of the skirt on account of its thermal expansion attributable to the heat conducted to it from the head, but rather due to the radial forces created by the very great thermal expansion radially of the head.

In my earlier invention I have shown the means now widely followed to permit the snug fitting of a piston skirt within the cylinder, thus eliminating piston slap at all speeds and temperatures of the engine, and at the same time insuring against seizure, or piston or cylinder scoring, or both. On further analysis of the problem, I concluded that such a piston might be fitted successfully even more closely within the cylinder if the piston skirt were properly relieved. Relief may be termed an exterior peripheral under-cutting of the portions of the piston skirt so that such portions will not come into contact with the cylinder wall. In view of the radial expansion of the head, each element of the complete or incomplete cylinder, which is the piston skirt, would tend to move radially outward from the upper or head end of the skirt in decreasing measure to the bottom of the skirt or open end, except where the con tinuity of the elements from piston head to skirt is broken physically which is actually the case with all elements lying between the element intercepted by the chord of the are representing the extent of the circumferential separating slot. However, due to the rigidity of the piston structure in general, the relief circumferentially should extend well beyond the elements in question, that is, Well over onto the peripheral surface of the independently functioning portions of the piston skirt.

My previous invention was based 1922. Serial No. 563,782.

In other words, the elements bounding the circumferential extent of the relief, extends beyond the elements cut by the circumferential separating groove or slot with,

respect to their respective circumferential distances from the piston pin axis. This is true, not oniy of the exact piston structure shown in my atent No. 1,153,902, but in cases where the ribs are replaced by other means such as webs, or struts connecting or supporting the independently functioning parts of the skirt with respect to the other portions of the piston. In those cases where there is a rigid strut or web transversely across the wrist pin boss, it is increasingly necessary to carry this relief well beyond'the intercepted element since in those cases the actual lengthwise expansion of the webs or struts due to the heat conducted thereto from the 0 head.

My theory has been substantiated in every respect in that I find I can, fit a piston with considerably less clearance with the relief as indicated than is possible with the relief not extending beyond the elements in question. In one particular case-it was possibleto reduce the clearance, from .005" to .003", Whereas with an ordinary piston, that is one not constructed in accordance with my original patent, a clearance of .009" to .010" was necessitated,

In the accompanying drawings, Fig. 1 shows a front elevation of a piston constructed with the relief designed in accordance with this invention.

Fig. 2 is a side elevational view of the piston shown in Fig. 1.

Fig. 3 is a sectional view of a piston of the type shown in my prior patent externally re- {ieved in accordance with my present inven- Fig. 4 shows the application of my present invention to a construction in which struts or webs take the place of the radial ribs shown in my previously mentioned prior patent.

Fig 5 shows the application of my present invention to a construction in which the relief takes the form of an actual change in the contour of the piston and in which the independently functioning portions of the skirt are supported from struts or webs that take the place of the radial ribs shown in my prior patent.

Fig. 6 is a view in perspective of a piston of somewhat different form illustrating an additional application of my invention.

Fig. 7 is a front elevational view of a piston having its relieved area extending to the bottom of the skirt in accordance with this invention.

Fig. 8 is a side elevational view of the piston shown in Fig. 7; and

Fig. 9 is a View in perspective of a piston of the form shown in Fig. 5 with the relief extending to the bottom of the piston skirt.

Referring to the drawings, 1 in all cases is the piston head. 2 is the piston skirt. 3 is the relief. 4 is a circumferential separatingslot. For our purposes the piston head is to be considered the part above the circumferential slots, the skirt the part below it. 5 represents a longitudinal slot or groove, 6 represents the rib, web or strut forming the support of the independently or partially independently functioning portions of the skirt. It will be noted that the relief 3 in all cases is carried well beyond the supporting or attaching medium 6. The portions of the piston skirt adjacent to the wrist pin bosses and physically integral with the piston head are subject to the mechanical expansion produced by the thermal expansion of the head 1, and this expansion-acts radially in all directions, ancLall elements on skirt 2, will be moved mechanically outward except where the elements are out, due to the rigidity of the supporting medium 6; these will'be moved outwardly also for some little distance past the point where the elements are actually out by the circumferential slot 4. In practice the length of the chord subtending this circumferential slot will vary, but in all cases, relief 3 should extend well beyond it. Chords 77 show the arc subtended by the circumferential slot 4 in the cases represented by Fig, 4- and Fig. 5.

It is not my purpose to confine my invention to any particular form of relief. This may be a reduced diameter, or there may be an actual change in the contour of the piston at this point, or this relief may be a maximum adjacent and opposite the wrist pin bosses gradually decreasing to nothing at the proper point beyond the elements cut by aforesaid circumferential slots.

What I claim as new and desire to claim by Letters Patent is:

l. A piston for an internal combustion engine, comprising, a head and a skirt, piston pin bosses projecting from the interior of said skirt, said skirt having longitinlinally disposed grooved ribs arranged between said wrist pin bosses and the cylinder engaging walls of the skirt having its cylinder wall engaging section separated from said head by circumferentially arranged slots, the external surface of said skirt being relieved continuously and from points opposite said wrist pin bosses to points beyond the walls of said longitudinal groove at either side of each said boss.

2. A piston for an internal combustion engine, comprising, a head and a skirt, piston pin bosses projecting from the interior of said skirt, said skirt having longitudinally disposed grooved ribs arranged between said wrist pin bosses and the cylinder engaging walls of the skirt having its cylinder wall engaging section separated from said head by circumferentially arranged slots, the walls of said skirt being relieved continuously from points intermediate said cylinder engaging sections and the wall adjacent one of said grooves toward the vertical plane of the axis of the adjacent pin boss.

3. A piston for an internal combustion engine comprising a head portion having a ring flange depending therefrom, and a skirt portion having oppositely disposed cylinder bearing portions with boss carrying portions intermediate said cylinder bearing portions and joined thereto by web portions, each of said boss carrying portions being integrally joined to the head portion, each of said cylinder bearing portions being separated from the head portion by a circumferential slot formed adjacent said ring flange and terminating at the connection of said boss portion to said head portion, the skirt portion being substantially relieved in the zone of each of said boss portions over an area including the web portions adjacent each of said boss portions.

4. A piston for an internal combustion engine comprising a head portion having a ring flange depending therefrom, and a skirt por tion having oppositely disposed cylinder bearin )ortions and boss carrvin ortions e h I intermediate said cylinder bearing portions and joined thereto by web portions, each of said boss carrying portions being integrally joined to the head portion, each of said cylinder bearing portions being separated from the head portion by a circumferential slot formed adjacent said ring flange and terminating at the base of said. boss portion, the

cylindrical surface of said skirt portion being substantially relieved in the zone of each of said boss portions over an area extending beyond the terminae of the said circumferential slots on the corresponding side of said skirt.

5. A piston for an internal combustion engine comprising a head having a ring flange depending from the periphery thereof, a skirt having oppositely disposed cylinder engaging walls-and oppositely disposed wrist pin carrying sections arranged between said cylinder engaging walls and integrally connected to said head, the skirt section being separated from the head section by ciroumferential slots extendin at either end beyond the adjacent boundaries of said cylinder engaging walls, webs connecting the cylinder engaging walls and the boss carrying sections, the skirt section being relieved on opposite sides over areas includingthe Web sections and adjacent wrist pin bosses and said circumferential slots extending into said relieved areas at either side of the piston.

6. A piston for internal combustion en-.

gines having in combination a head section and a guide section comprising diametrically opposite cylinder engaging portions separated from the head section by air gaps and intermediate portions formed with wrist pin bosses and connected at their upper ends to the head sections, said intermediate portions also being formed to have no contact with the cylinder from their upper ends to points below the bosses and being adapted when the head expands to apply stresses to said cylinder engaging portions in a manner tending to draw them toward each other. a

7. A piston for internal combustion engines having a head and a sleeve, transverse slots in diametrically opposite sides of the piston separating the opposite side portions of the head from the sleeve, whereby the head is connected to the sleeve between the ends of the slots, the sleeve being slightly elliptical in general form in cross section, the ends of the elliptical form being concentric with the axis of the piston, and wrist pin bosses projecting from the portions of the sleeve joined to the head between the ends of the slots, the axis of said pin bosses extending along the short diameter of the elliptical form, substantially as and for the purpose specified.

8. A one piece piston comprising a head and a skirt, the skirt having boss carrying portions exteriorly relieved and arranged opposite each other and secured to the head by substantially rigid connectors to cause radially outward and inward movement of the portions under operation conditions of the piston, the skirt also having opposite bearing wall portions arranged between the said boss carrying portions and each separated from the head by a slot, of greater circumferential length than the corresponding length of the said portions. 7

9. A piston comprising ahead and a substantially continuous skirt connected thereto, the skirt having boss carrying wall portions, exteriorly relieved, and bearing wall portions, each bearing wall portion being separated from the head by a slot extending not less than about 10 beyond either side of the said portion.

10. A piston comprising a head and a substantially continuous skirt connected thereto, the skirt having boss carrying wall portions, exteriorly relieved, and bearing wall portions approximately 60 in circumferential length, each bearing wall portion being separated from the head by a continuous circumferential slot extending not less than about 10 beyond-either side of the said portion.

11. An integrally formed piston for internal combustion engines comprising in combination a head portion having a circumferentially depending ring flange, a guide portion having diametrically opposite cylinder engaging parts for'taking the angularthrust of a connecting rod, each being circumferentially separated from said ring flange, op-

positely disposed wrist pin bosses depending from said head portion and extending between adjacent longitudinal ends of said cylinder engaging parts, and integral webs extending between said adjacent longitudinal ends and being integral with said bosses, each of said cylinder engaging parts being circumferentially extended beyond the connections of said webs therewith, and each being circumferentially relieved on its exterior surface from its extreme longitudinal edges to points substantially beyond the 'connections of said webs therewith.

12. An integrally formed piston for internal combustion engines comprising in combination a head portion having a circumferentially depending ring flange, a guide portion having diametrically opposite cylinder engaging parts for taking the angular thrust of a connecting rod, each being separated from said ring flange by a circumferential slot, oppositely disposed wrist pin bosses depending from said ring flange and extending between adjacent longitudinal ends of said cylinder engaging parts, and a pair of longitudinal parallel Webs, integral with said wrist pin bosses, each extending between adjacent longitudinal ends of said cylinder engaging parts perpendicular to the axis of said wrist pin bosses, and each being 1nte grally connected with said ends a substantial distance from the marginal edges thereof, each of said cylinder engaging parts being ieo exteriorly relieved from said longitudinal ing a packing ring supporting portion, a cylinder engaging portion, comprising oppositely disposed circumferential sections separated from said ring supporting portion by circumferential slots, a pair of wrist pin bearings depended from said ring supporting portion separated from said cylinder en head having a ring flange, a longitudinal skirt having oppositely disposed boss carrying portions integral with said ring flange and opposite bearingwall portions between said boss carrying portions, each bearing wall portion being separated from said ring flange by a circumferential slot of greater length than the corresponding length of the said portion, wrist pin bosses extending inwardly from said boss carrying portions, reinforcing ribs extending longitudinally within said skirt adjacent each side of each of said wrist pin bosses, and longitudinal slots in the external surface of said skirt extending into each of said ribs, the external surface of said skirt being relieved continuously and from points opposite said wrist pin bosses to points beyond the Walls of said longitudinal slot at each side of each of said bosses.

15. In an internal combustion engine, a head having a ring flange, a longitudinal skirt having oppositely disposed boss carrying portions integral with said ring flange and opposite bearing wall portions arranged between said boss carrying portions, each bearing wall portion being separated from said ring flange by a circumferential slot of greater length than the corresponding length of the said portion, wrist pin bosses extending inwardly from said boss carrying portions, reinforcing ribs extending longitudinally within said skirt adjacent each side of each of said wrist pin bosses, and longitudinal slots in the externalsurface of said skirt extending into each of said ribs, the slots at one side of said bosses extending from the open end of said skirt to the ends of the said circumferential slot at that side, and the slots at the other side of said bosses extending from the open end of said skirt to the ends of the other of said circumferential slots, the external surface of said skirt being relieved continuously and from points opposite said wrist pin bosses to points beyond the walls of said longitudinal slot at each side of each of said bosses.

16. In an internal combustion engine, a head having a ring flange, a longitudinal skirt having oppositely disposed boss carrying portions integral with said ring flange and opposite bearing wall portions between said boss carrying portions, each bearing wall portion being separated from said ring flange by a circumferential slot of reater length than the corresponding length of the said portion, wrist pin bosses extending inwardly from said boss carrying portions, reinforcing ribs extending longitudinally within said skirt adjacent each side of each of said wrist pin bosses, and longitudinal slots in the ex ternal surface of said skirt extending into each of said ribs, the external surface of said skirt being relieved the full length thereof and continuously from points opposite said Wrist pin bosses to points beyond the walls of said longitudinal slot at each side of each of said bosses.

In testimony whereof, I affix my signature.

GUSTAVE E. FRANQUIST. 

